In liquid product packaging, e.g. in liquid food packaging, a carton-based packaging material is often used for forming the final packages. FIG. 1 shows an example of such a system. The packaging material may be provided as single sheets for creating individual packages in a filling machine, or as a web of material which is fed into a filling machine. The web of packaging material is normally distributed in large rolls 7 of which the filling machine is configured to feed the packaging material 3 through various treatment stations, such as sterilizers, forming sections 8, filling sections 10, and distribution sections of the filling machine.
The packaging material may be formed into an open ended tube. The tube is arranged vertically in the filling machine 10 and is subject to continuous filling as the packaging material is transported through the filling machine. As the packaging material, and thus the tube, is moving transversal seals 14 are provided for forming individual packages of the tube. Each package is separated from the tube by a sealing jaw 14 operating to also provide a transversal cut in the sealing area, and the individual packages 15 are transported for allowing subsequent packages to be separated from the tube.
The tube is formed by arranging the lateral ends of the packaging material such that they overlap, and by sealing the lateral ends to each other for creating a fluid tight connection between the lateral ends.
Induction heating devices for transversal sealing are commonly made up of five individual components, as shown in FIG. 2. A base structure 201 usually being made of aluminium supports a mounting core 202 which is typically made of polyphenylene sulfide (PPS). A number of inserts 203 of soft magnetic material are provided on the mounting core, for locally boosting the magnetic field of the induction heating device and thereby boosting the induced power at the conductive layer of the package leading to a local increase in power of approximate 30%. A coil 204 is arranged adjacent to the inserts 203, and finally a body structure 205 encases all of the other components. Similarly to the mounting core 202, the body structure 205 may be made of PPS. Normally such inductor heating device 20 is manufactured by mounting the base structure 201, the core 202, the insert(s) 203 and the coil 204 together in a mould, followed by injection moulding the body structure 205 over the mounted components.
Until today the magnetic inserts 203 are manufactured by sintering a soft magnetic material into rigid pieces. The sintering process is a very costly method, requiring advanced equipment while restricting the design freedom for the shape of the inserts 203.
Further to this known induction heating devices have limited life time expectancy. Over time the body structure becomes fatigued due to the intermittent pressing action towards the roll of packaging material which is required to provide the transversal seal.
Hence, an improved solution for magnetic inserts as well as induction heating devices utilizing such magnetic inserts would be advantageous.